Changing fluorescent fixture from T12 to T8

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Old 10-15-16, 01:53 PM
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Changing fluorescent fixture from T12 to T8

Hello all. I recently bought a complete T8 fixture with ballast to replace my T12 dinosaur. I just took some pictures of the old fixture and ballast and the wiring. I wasn't exactly sure the wire setup I see. Ive installed my own switches and fixtures quite a bit but never a florescent fixture. If anyone could maybe give me some wiring scenarios on these pictures it might help me with putting up new one. I haven't removed the fixture yet but i see 2 black wires coming into fixture from house wiring. I do notice one of them is attached to the white neutral going into ballast. I wanna guess that they have run a switch leg to switch but Ive found some odd things in this older house. Any tips or pointers would be great. I can also take a look at switch. Thank you
 
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Old 10-15-16, 02:04 PM
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If you are just replacing the entire fixture with a new one, the only wires you need to be concerned about are the two entering the fixture from the ceiling. They go to the two line voltage wires on the new ballast, usually white and black. Normally you would have a white and black from the house wiring, but in older houses you see a lot of non standard wiring. Just connect the two black wires to the white and black from the new ballast and it should work. Doesn't matter which goes to which.

If you have a ground wire in the box above the fixture (green or bare) it should connect to the ground screw on the new fixture (usually marked green).
 
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Old 10-16-16, 12:47 AM
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Can anyone please explain why there is only 2 black wires coming out of ceiling so I know etc. And would it be possible somehow to keep fixture on ceiling and use the t8 parts or put t8 fixture inside this t12 one ill post pics of each

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Last edited by ray2047; 10-16-16 at 12:54 AM. Reason: Properly space images.
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Old 10-16-16, 01:00 AM
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Can anyone please explain why there is only 2 black wires coming out of ceiling so I know
There should be a white. Please give us a close up of the wires coming into the bottom picture fixture.

Please give us a picture of the wires coming into the top fixture picture. Remove the cover if necessary.
 
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Old 10-16-16, 02:13 AM
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Well one problem is that they have nailed the old fixture into ceiling not screws and its solid which is why i thought leaving it there also i dont know if the popcorn ceiling is under it. But here is 2 pics. I did notice they have a white and black capped togetherName:  tmp_27168-20161016_0205292119999902.jpg
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Old 10-16-16, 02:17 AM
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Here is the switch also 2 blacks Name:  tmp_27168-20161015_003200952655093.jpg
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Old 10-16-16, 06:49 AM
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Yes, you can keep the existing fixture. Just return the new fixture and buy a 2 lamp T8 ballast. Remove the old ballast and wire the new ballast according to the wiring diagram on the new ballast. New ballast will likely only run you about $15. The new T8 lamps will fit the T12 sockets.
 
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Old 10-16-16, 12:23 PM
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Assuming of diffuser lens of the old fixture is in good condition, I'd agree that simply replacing the ballast is the better option. That new fixture looks like a cheaper wraparound without a channel cover. The consequence of no channel cover is that the ballast requires sleeved leads, which makes replacing the ballast later on more difficult. Also, if the T12s still work, consider whether the energy savings are great enough to make a difference on your electric bill. With light usage, the savings may be negligible.

Another consideration is how frequently the lights are switched on and off. If frequently switched, a T8 programmed start ballast is the best choice. In frequently switched applications, T8s on an instant start ballast may not last as long as T12s on the old rapid start ballast. However, T8s on programmed start, particularly the extended life lamps, will outlast either.

Often in residential settings where lights are switched on and off multiple times each day, you find standard T8s on instant start ballast, which aren't the best fit. Instant start ballasts do tend to be cheaper and more readily available, however. For applications where the lights are on more than three hours or so per start, the advantages of programmed start over instant start begin to lessen. LED tubes are another option to think about, and lamp life of LED lamps are not affected by frequent starting.
 
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Old 10-16-16, 12:39 PM
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Another point, some of the fixtures like the new one pictured in this thread require that wire connections be made within a junction box. Therefore you cannot install it and be up to code unless you have a ceiling box. Although the channel cover of the old fixture is removed in the pictures, it appears to be the type that has one and therefore it is acceptable for the splices to be made within the fixture itself, and hence no box is necessary.
 
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Old 10-16-16, 12:40 PM
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The reason you have two black wires coming into the fixture is more than likely because there is a junction box in the ceiling so the wiring was extended to reach the fixture. That fixture may or may not be grounded.
 
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Old 10-16-16, 03:06 PM
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some of the fixtures like the new one pictured in this thread require that wire connections be made within a junction box.
I have never seen a fluorescent fixture that does now allow splicing inside the fixture. They do require any wire to be 90 degree rated though.
 
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Old 10-16-16, 05:14 PM
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Yes there is a box above with peek i took. Couldnt i just put the t8 ballast in that fixture and wire it the same? The tombstones should work with either bulb right?
 
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Old 10-16-16, 06:30 PM
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Couldnt i just put the t8 ballast in that fixture and wire it the same?
For AC power in yes but all other wiring is different. You must follow the wiring schematic on the new ballast.

Comparison of typical T-12 to T-8:

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Note: Your wiring may vary.
 
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Old 10-16-16, 08:05 PM
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Ya the new one has blue on 1 tombstone 1 red on other beside it. The other end just has 2 tombstones connected with single white wire. But my old one is like that diagram. Its just puzzling haveing the black spliced into white in fixture like it is.
 
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Old 10-16-16, 08:16 PM
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Its just puzzling haveing the black spliced into white in fixture like it is.
Who ever ran the wires didn't know he was wrong or didn't care.
 
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Old 10-16-16, 09:24 PM
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My only thought or experience seeing or doing that was running a switch leg from fixture to a new switch. I guess Ill have to take down old fixture and get a better look. And since i have the t8 fixture and tubes already i dont know what best option is. My old t12 finally accepted the 2x 40w bulbs i bought so ill use it for now i guess.
 
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Old 10-17-16, 03:16 AM
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I would really like to try the new t8 fixture and see how it looks and how bright it is etc. What would be your guys first course of action. I would try and keep wiring similar as through my experience once i mess around with wiring it can create other problems and the wiring in this house is old and I don't want to affect anything else in this circuit loop.
 
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Old 10-18-16, 09:48 PM
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So without tearing the ceiling apart or fixture i was able to see ceiling box underneath the florescent fixture. There is a black and white wire in box. The white is capped with a black going into fixture and the black wire in box is capped with a black that is going to a white in fixture. I have no idea why or whats going on. The switch has 2 blacks only. What should i do check black and white wires in the box to see which is main power etc as that setup i saw doesnt make sense
 
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Old 10-18-16, 11:47 PM
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Switch the black pigtail fastened to the white wire to a white pigtail. Is there a ground in the box? if so a green pigtail should be connected to it.
The switch has 2 blacks only.
And if you look closely two whites connected only to each other. If so that is normal and expected when power comes in at the switch.
 
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Old 10-19-16, 12:52 AM
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Yea i knew the switch was normal the one with 2 blacks is the switch and yes the neutral between both switches is connected as you said. and not a switch leg as that was what i had to install the othe day. I just dont know why the fixture was wired like that. I know the fixture isnt grounded so i hope the box above it is. I couldn't totally take fixture down to check. Its like he ran put of wire perhaps in the box above?
 
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Old 10-19-16, 01:28 AM
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I see a ground wire in the switch box. Does that come from power in? Is the power out to the light cable a cable with no ground wire?

Besides safety the issue with no grounds is fluorescent lights tend to have a harder time starting though not so much a problem with newer ballasts.
 
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Old 10-19-16, 03:27 AM
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There's ground wires in the switch boxes yes. Im not 100% but i think power enters switch first. I will have to rip fixture down to get better look. And by then ill prob just utilize the t8 fixture and tubes i got here. Tbis house has many bad or lazy wiring jobs. My sons light fixture had no caps and wires were held together with hockey tape...not electrical ugh
 
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Old 10-19-16, 03:43 AM
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If by hockey tape you mean friction tape there is a long history to that. Originally splices were wrapped with rubber tape then the rubber tape was wrapped with friction tape. Some old timers just skipped the rubber tape and used friction tape. (Or maybe saw splices with friction tape and didn't know rubber tape was used underneath.)
 
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Old 10-19-16, 03:47 AM
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Whats scary is besides the stove and dryer my whole basement suite runs on 2 circuits only. Im slowly replacing and making everything safer where i can. And learning along thw way lol
 
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